US7011684B2 - Intervertebral disk prosthesis - Google Patents

Abstract

An intervertebral disk prosthesis includes a first part, and the first part has a top, a bottom having an opening, an outer surface, an inner surface and a socket extending into an interior of the first part from the opening and defined by the inner surface. The outer surface proximate the top contacts a concave portion of a first vertebra. The disk prosthesis further includes a second part including a top, a bottom, and an outer surface. The outer surface proximate the bottom contacts a concave portion of a second vertebra, and the outer surface of the second part proximate the top of the second part cooperatively engages the inner surface of the first part thereby allowing at least two-degrees of freedom of movement.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/369,667 filed Apr. 2, 2002 entitled “DISK PROSTHESIS” and U.S. Provisional Application No. 60/349,743 filed Jan. 17, 2002 entitled “DISK PROSTHESIS,” the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for intervertebral disk replacement and more particularly to an intervertebral disk prosthesis capable of being implanted in a patient utilizing minimally invasive surgical techniques.

Referring to prior artFIGS. 9 and 10, thespine120, also known as the vertebral column or the spinal column, is a flexible column of vertebrae100 (special types of bones) held together by muscles, ligaments and tendons. Thespine120 extends from the cranium (not shown) to thecoccyx126, encasing aspinal cord128 and forming the supporting axis of the body (not shown). Thespinal cord128 is a thick bundle of nerve tissue (nerves) that branch off to various areas of the body for the purposes of motor control, sensation, and the like. Thespine120 includes seven cervical vertebrae (not shown), twelve thoracic vertebrae (not shown), five lumbar vertebrae, L^I–L^V, five sacral vertebrae, S^I–S^V, and threecoccyx vertebrae126. The sacral and coccyx vertebrae are each fused, thereby functioning as a single unit.FIG. 10 shows thelumbar region122, thesacral region124 and thecoccyx126 of thespine120 and that thevertebrae100 are stacked one upon another. Thetop portion100aandbottom portion100bof eachvertebrae100 is slightly concave. The opposing concave vertebral surfaces form theintervertebral space121 in which an intervertebral disk (not shown) resides. Each of the intervertebral disks has a soft core referred to as a nucleus pulposus or nucleus (not shown).

InFIG. 9,directional arrow101ais pointing in the posterior direction anddirectional arrow101bis pointing in the anterior direction.FIG. 9 shows that eachvertebrae100 includes abody106 in the innermost portion, aspinal canal108 and aspinous process102 at the posterior-most end of thevertebra100. Thevertebrae100 are substantially similar in composition, but vary in size from the larger lumbar vertebrae to thesmallest coccyx vertebrae126. Eachvertebrae100 further includes twotransverse processes104 located on either side and a protective plate-like structure referred to as alamina10. Nerves from thespinal cord128 pass through thespinal canal108 andforamina111 to reach their respective destinations within the body.

The natural aging process can cause a deterioration of the intervertebral disks, and therefore, their intrinsic support strength and stability is diminished. Sudden movements may cause a disk to rupture or herniate. A herniation of the disk is primarily a problem when the nucleus pulposus protrudes, bulges or ruptures into thespinal canal108 placing pressure on nerves which in turn causes spasms, tingling, numbness, and/or pain in one or more parts of the body, depending on the nerves involved. Further deterioration of the disk can cause the damaged disk to lose height and as bone spurs develop on thevertebrae100, result in a narrowing of thespinal canal108 and foramen111 (not shown clearly), and thereby causes pressure on the nerves emanating from thespinal cord128.

Presently, there are several techniques, in addition to non-surgical treatments, for relieving the symptoms related to intervertebral disk deterioration. Surgical options include chemonucleolysis, laminectomy, diskectomy, microdiskectomy, and spinal fusion.

Chemonucleolysis is the injection of an enzyme, such as chymopapain, into the disk to dissolve the protruding nucleus pulposus. The enzyme is a protein-digesting enzyme and is used to dissolve the disk material. Since the enzyme is essentially a tissue-dissolving agent, it is indiscriminate in the protein-based matter it dissolves. Should the enzyme be injected into the wrong place, or if there is a breach in the disk capsule that would allow the solution to enter the spinal canal or to contact nerve tissue or the like, the resultant damage to nerve tissue could not be reversed. Even worse, about half of the patients who receive chemonucleolysis treatments experience increased back pain and muscle spasms immediately after the injection and more than half have incapacitating back pain for durations up to three months after such treatments.

A laminectomy is performed to decompress thespinal canal108 by open surgical techniques under general anesthesia. In this procedure, thelamina110, (the bone that curves around and covers thespinal canal108 as shown inFIG. 9), and any disk tissue causing pressure on a nerve or thespinal canal108, are partially removed. This technique is highly invasive and traumatic to the body, and therefore requires an extended recovery time of about five weeks and a hospital stay of a few days. In addition to the trauma inflicted on the body from even a successful surgery, there are increased risks of future problems due to the removed portion of thelamina110 which is no longer in place to support and protect thespinal canal108 at the area where the surgery took place. Further, thevertebrae100 may shift due to the lack of support in the structure. Thus, simply removing the disk and parts of the vertebral bone is a short-term, pain-relieving corrective action but not a long-term solution.

Diskectomy is a form of spinal surgery wherein part of an intervertebral disk is excised typically through open surgical techniques. Recently, less invasive techniques referred to as percutaneous diskectomy or microdiskectomy have been developed to reduce the surgical trauma to the patient. In microdiskectomy, a much smaller incision is made than in normal open surgeries. A small retractor, working channel or tube is inserted through the posterior muscles (not shown) to allow access to the intervertebral space of a damaged or herniated disk. Surgeons utilize special surgical instruments modified to work in such small openings such as curettes, osteotomes, reamers, probes, retractors, forceps, and the like to cut and remove part of the disk while monitoring their technique using a microscope, a fluoroscope (real-time X-ray monitoring), and/or an endoscope (a miniature TV camera with associated viewing monitor). While this technique is much less invasive than conventional open surgeries, due to their design the instruments presently available tend to extend the length of time of the surgery and may cause possible damage to areas other than the herniated disk.

The removal of a significant amount of disk material or numerous surgeries often increases the instability of thespine120 thereby necessitating spinal fusion surgery. In a fusion procedure, a damaged disk may be completely removed. Parts of a bone from another part of the body, such as the pelvis, are harvested, and the bone parts or grafts are subsequently placed between theadjacent vertebrae100 so that theadjacent vertebrae100 grow together in a solid mass. In the fusion surgery, which is presently performed as an open surgical technique, theposterior lamina110 and the centers of thevertebral bodies106 may both be cut. The surgery often involves consequential damage to the associated posterior ligaments, muscles and joints in addition to the removal of part or all of thelamina110. The recovery time for a normal spinal fusion surgery is significant due not only to the fact that normal movement cannot be allowed until detectable bone growth has occurred between the bone grafts and theadjacent vertebrae100, but the associated ligaments, muscles and the location where the bone grafts were harvested must also recover. Oftentimes portions of thespine120 must be immobilized during the recovery period causing added discomfort and inconvenience to the patient.

A relatively new concept (within the past two decades) is intervertebral total disk replacement or nucleus pulposus (nuclear) replacement. Nuclear replacements are generally designed with either a water retaining chemical in a compartment (bag-like container) or with various woven fiber or pad configurations using synthetic materials as a support cushion. In concept, nuclear replacements have significant potential because the annulus and the endplates are substantially preserved, so long as they were not damaged by previous trauma. However, to date, the available nuclear replacements lack the strength of a human disk nucleus pulposus matter and/or the damage to the annulus during implantation may allow extrusion of the nuclear replacement not unlike a disk herniation.

The prior art devices for total disk replacements are generally made with opposing metal bodies and an interstitial polyethylene plastic body or the like. The greatest difficulty to date has been designing a mechanical structure that closely matches that of the human intervertebral disk with regard to such properties as compression, flexion, extension, torsion and the like, not to mention in endurance/durability. Further, prior art intervertebral disk implants are typically as large as a human intervertebral disk so as to match thevertebrae100 thereby distributing the compressive loads over a greater area, but necessitating extensive open surgery. Even worse, critical support materials, such as the ligaments andendplate110, are usually cut away during the surgical procedure leaving the newly implanted disk replacement with less stability.

What is required, but not presently provided by the prior art devices and methods, is a device for replacing damaged, failed, and/or removed intervertebral disks that is able to be implanted in a minimally invasive procedure, is easy to use, safe to insert into the body during surgery, and which allows a range of motion in adjacent vertebrae similar to that of the human intervertebral disk. What is further required is an artificial disk or disk prosthesis that allows for rapid patient recovery times and that can be used on an outpatient basis.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, the present invention comprises an intervertebral disk prosthesis. The disk prosthesis includes a first part having a top, a bottom having an opening, an outer surface, an inner surface and a socket extending into an interior of the first part from the opening and defined by the inner surface. The outer surface proximate the top contacts a concave portion of a first vertebra. The disk prosthesis further includes a second part including a top, a bottom, and an outer surface. The outer surface proximate the bottom contacts a concave portion of a second vertebra, and the outer surface of the second part proximate the top of the second part cooperitively engages the inner surface of the first part thereby allowing at least two-degrees of freedom of movement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 is a perspective view of a disk prosthesis in accordance with a first preferred embodiment of the present invention;

FIG. 2 is a side elevational view of the disk prosthesis ofFIG. 1;

FIG. 3 is a front elevational view of the disk prosthesis ofFIG. 1;

FIG. 4 is a top plan view of the disk prosthesis ofFIG. 1;

FIG. 5 is a side sectional view of the disk prosthesis ofFIG. 1;

FIG. 6A is a side sectional view of a second preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 6B is a side sectional view of a third preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 6C is a side sectional view of a fourth preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 7A is a side elevational view of the disk prosthesis ofFIG. 6A connected to a first insertion tool;

FIG. 7B is a side elevational view of the disk prosthesis ofFIG. 6A connected to a second insertion tool;

FIG. 7C is a side elevational view of the disk prosthesis ofFIG. 6A connected to a third insertion tool;

FIG. 8 is a side view of the lumbar section of a human spine with a disk prosthesis shown not to scale installed between vertebra L^IIIand vertebra L^IV;

FIG. 9 is a top sectional view of a human vertebra as is known in the art;

FIG. 10 is a side sectional view of a portion of a human spine as is known in the art;

FIG. 11A is a side elevational view of a fifth preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 11B is a front elevational view of the disk prosthesis ofFIG. 11A;

FIG. 12A is a side elevational view of a sixth preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 12B is a front elevational view of the disk prosthesis ofFIG. 12A;

FIG. 13A is a side elevational view of a seventh preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 13B is a front elevational view of the disk prosthesis ofFIG. 13A;

FIG. 14A is a side elevational view of an eighth preferred embodiment of a disk prosthesis in accordance with the present invention;

FIG. 14B is a front elevational view of the disk prosthesis ofFIG. 14A;

FIG. 15A is a side elevational view of a fourth insertion tool for a disk prosthesis in accordance with the present invention;

FIG. 15B is a top plan view of the insertion tool ofFIG. 15A;

FIG. 16A is a side elevational view of a fifth insertion tool for a disk prosthesis in accordance with the present invention; and

FIG. 16B is a top plan view of the insertion tool ofFIG. 16A.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower”, and “upper” designate directions in the drawing to which reference is made. The words “inwardly” and “outwardly” refer direction toward and away from, respectively, the geometric center of the disk prosthesis and designated parts thereof. The terminology includes the words above specifically mentioned, derivatives thereof and words of similar import. Additionally, the word “a”, as used in the claims and in the corresponding portions of the specification, means “at least one.”

Referring to the drawings in detail, wherein like reference numerals indicate like elements throughout, there is shown inFIG. 1 an artificial disk ordisk prosthesis10 having adistal end10a, aproximal end10b, alower wall10c, anupper wall10d, afirst sidewall10eand asecond sidewall10f(FIGS. 3,4). Thedisk prosthesis10 includes a first part or acap13. Thecap13 includes a top13d, a bottom13chaving anopening13f, anouter surface13a, and with reference toFIG. 5, aninner surface13band asocket13eextending into an interior of thecap13 from theopening13fand defined by theinner surface13b. Theouter surface13aproximate the top13dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis10 further includes a second part or a base11 including a top11d, a bottom11c, and anouter surface11a. Theouter surface11aproximate the bottom11ccontacts aconcave portion100aof a asecond vertebra100, and the outer surface of the base11 proximate the top11dof the base11 cooperatively engages theinner surface13bof thecap13 thereby preferably allowing at least two-degrees of freedom of movement.

As shown inFIG. 8, when inserted into anintervertebral space121 thecap13 and the base11 function together as one overall device, i.e., thedisk prosthesis10. However, it should be noted that thecap13 and the base11 are preferably not mechanically connected. In alternate embodiments thecap13 and the base11 are connected by a flexible structure or element (not shown) or are totally encased in a pliable, bio-compatible slip-cover or pouch (not shown). Theinner surface13band aportion11eof theouter surface11athat contacts theinner surface13bare preferably formed of or coated with a bio-compatible, smooth, low-friction material with high durability, such as ceramic, an alloy or the like.

Together, theouter surface13aof thecap13 and aportion11bof theouter surface11aof the base11 that is not covered by thecap13 comprise anouter prosthesis surface12 that is substantially smooth over the entire surface. The structure of theprosthesis10 is preferably a bio-compatible metal, a bio-compatible alloy or a bio-compatible ceramic. However, the structure may be titanium, stainless steel, alloys such as a cobalt-chrome molybdenum alloy, polymeric materials, composites, and the like without departing from the broad inventive scope of the present invention.

Thedisk prosthesis10 preferably is generally ovoid or egg-shaped and symmetrical along the longer axis with rounded or contoured edges on all sides. Thelower wall10candupper wall10dpreferably are generally convex in order to cooperatively mate with the natural concavity ofadjacent vertebrae100. Similarly, thefirst sidewall10eandsecond sidewall10fof thedisk prosthesis10 preferably are similarly convex for similar reasons and to facilitate installation of thedisk prosthesis10 into anintervertebral space121. The overall shape of the disk prosthesis is such that it can be inserted into anintervertebral space121 using minimally invasive techniques through a special portal or channel allowing disk arthroplasty on an outpatient basis. In an alternate embodiment of the first preferred embodiment, theproximal end10bis rounded but more bluntly-shaped than thedistal end10awhich is sloped into a bullet-shaped tip.

Thelower wall10cpreferably includes alower mesh structure16aand theupper wall10dof thedisk prosthesis10 preferably includes anupper mesh structure16bat the point of vertebral contact to encourage successful vertebral bone ingrowth thereby affixing thecap13 to a first orupper vertebra100 and the base11 to a second orlower vertebra100 in an adjacent pair ofvertebrae100. Thelower mesh structure16aand theupper mesh structure16bmay be a grid, a lattice, a plurality of perforations or apertures that extend partially through or completely through theouter surface12, or any other configuration capable of allowing vertebral bone ingrowth. Themesh structures16a,16bmay or may not be symmetrically-shaped. Themesh structures16a,16bare preferably identically-shaped with respect to one another and are preferably symmetrically-shaped, but need not be. It is contemplated that themesh structures16a,16bare each a larger aperture, or alternatively, are each a generally continuous section of a bio-compatible porous material such as hydroxyapatite coated metals or an irregular metal surface coated with hydroxyapatite coating. It is further contemplated that themesh structures16a,16bare not flush with the edges of theouter surface12, but are instead slightly below the edges of theouter surface12 to allow for subsidence of the vertebrae and greater bone ingrowth.

The length of the disk prosthesis as measured from thedistal end10ato theproximal end10bis approximately 10–30 mm, depending on the particularintervertebral space121 in which thedisk prosthesis10 is to be inserted. For example, the intervertebral space between lumbar vertebra L^IIIand lumbar vertebra L^IVfor an average male would accommodate adisk prosthesis10 of a length between approximately 25–30 mm. But, the length of thedisk prosthesis10 could vary from the aforementioned range without departing from the spirit of the invention.

The width of thedisk prosthesis10 as measured between thefirst sidewall10eand thesecond sidewall10fof thedisk prosthesis10 will vary from approximately 10 mm to 25 mm depending upon the particularintervertebral space121 in which thedisk prosthesis10 is to be inserted. For example, the intervertebral space between vertebra L^IIIand vertebra L^IVin an average male would accommodate adisk prosthesis10 having a width of approximately 15–20 mm. But, the width of thedisk prosthesis10 could vary from the aforementioned range without departing from the spirit of the invention.

The height of thedisk prosthesis10 as measured between theupper wall10dand thelower wall10cof thedisk prosthesis10 will vary from approximately 5 mm to 25 mm depending upon the particularintervertebral space121 in which thedisk prosthesis10 is to be inserted. For example, the intervertebral space between vertebra L^IIIand vertebra L^IVin an average male would accommodate adisk prosthesis10 having a height of approximately 8–16 mm. But, the height of thedisk prosthesis10 could vary from the aforementioned range without departing from the spirit of the invention.

FIG. 5 shows a side sectional view of thedisk prosthesis10 as viewed fromlines5—5 ofFIG. 4.FIG. 5 more clearly shows the cooperative interaction between thecap13 and thebase11. As mentioned above, aportion11eof theouter surface11aof the base11 proximate the top11dof the base11 cooperatively engages theinner surface13bof thecap13 thereby allowing at least two-degrees of freedom of movement. Motion allowed includes rotation (roll) and tilting or angulation (pitch) in any direction, but not motion in the plane from front to back or side to side (i.e., parallel to the disk space). Theinner surface13band theportion11eof theouter surface11athat contacts theinner surface13bare generally concealed.

The overall shape of thedisk prosthesis10 is designed for insertion using minimally invasive techniques through a special portal or channel allowing a replacement procedure to be implemented on an outpatient basis. The convex and contoured shape of thedisk prosthesis10 will allow thedisk prosthesis10 to be driven into anintervertebral disk space121 by merely temporarily distracting the vertebrae with minimal removal of the vertebral rim or annulus (not shown clearly) at the point of entry, thereby reducing the chance of dislodging the device post-surgery. The smooth contour and edges of thedisk prosthesis10 provide for a safe and easy entrance into theintervertebral space121.

Thedisk prosthesis10 is a self centering device. Due largely to the shape of thedisk prosthesis10, thedisk prosthesis10 will tend to find the natural concavity ofadjacent vertebrae100. As such, placement of thedisk prosthesis10 is much faster than that of prior art intervertebral disk replacement devices, thereby effectively reducing the duration of an intervertebral disk replacement procedure and the associated risks therewith. Further, the self-centering feature of thedisk prosthesis10 will allow rapid settling of thedisk prosthesis10 into adjacent vertebral bone to promote rapid bone ingrowth while retention of most of the annulus and peripheral rim of thevertebrae100 would provide good load sharing support to prevent excessive subsidence, where subsidence is the natural settling of intervertebral matter into a softer central portion of thevertebral bodies106.

FIG. 8 shows a side view of thelumbar region122 of a portion of ahuman spine120. In particular, thedisk prosthesis10 in accordance with the first preferred embodiment of the present invention is shown installed between lumbar vertebra L^IIIand lumbar vertebra L^IV. In this particular installation, thesecond sidewall10fof thedisk prosthesis10 is placed on the anterior side of the L^III–L^IVintervertebral space, thefirst sidewall10eof thedisk prosthesis10 is placed closest to the posterior side of the L^III–L^IVintervertebral space, theupper wall10dof thedisk prosthesis10 is adjacent to vertebra L^III, and thelower wall10cof thedisk prosthesis10 is adjacent to vertebra L^IV. In this example, the surgeon would have inserted thedistal end10aof thedisk prosthesis10 into the gap between the L^III–L^IVvertebrae as depicted inFIG. 9 by a directional arrow D. It is just as likely and possible for the surgeon to place thedistal end10aof thedisk prosthesis10 through the space between the L^III–L^IVvertebrae in the direction of a directional arrow C (FIG. 9) or from any other direction.

FIG. 6A shows a side sectional view of a second preferred embodiment of adisk prosthesis60 in accordance with the present invention. Thedisk prosthesis60 has adistal end60a, aproximal end60b, alower wall60c, anupper wall60d, afirst sidewall60e(FIGS. 7A–7C), and a second sidewall (not shown). The disk prosthesis includes a first part or acap63. Thecap63 includes a top63d, a bottom63chaving anopening63f, anouter surface63a, aninner surface63band asocket63eextending into an interior of thecap63 from the opening and defined by theinner surface63b. Theouter surface63aproximate the top63dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis60 further includes a second part or a base61 including a top61d, a bottom61c, and anouter surface61a. Theouter surface61aproximate the bottom61ccontacts aconcave portion100aof asecond vertebra100, and theouter surface61aof the base61 proximate the top61dof the base61 cooperatively engages theinner surface63bof thecap63 thereby allowing at least two-degrees of freedom of movement.

When inserted into anintervertebral space121 thecap63 and the base61 function together as one overall device, i.e., thedisk prosthesis60. Thecap63 and the base61 are preferably not mechanically connected. Thebase61 is preferably not retained in thecap63, but could be. In alternate embodiments thecap63 and the base61 are connected by a flexible structure or element (not shown) or are totally encased in a pliable, bio-compatible slip-cover or pouch (not shown). Theinner surface63band aportion61eof theouter surface61athat contacts theinner surface63bare preferably formed of or coated with a bio-compatible, smooth, low-friction material with high durability, such as a ceramic, an alloy or the like. The top61dof thebase61 includes a spherically or hemispherically-shaped portion or aball61f. Theball61fof the base61 cooperatively engages thesocket63eof thecap63 thereby mimicking a ball and socket joint such as a hip-joint. Obviously, other iterations and combinations of mutually cooperating engagement designs providing relative movement could be implemented without departing from the broad general scope of the present invention.

Thelower wall60cincludes alower mesh structure66aand theupper wall60dof thedisk prosthesis60 includes an upper mesh structure66bat the point of vertebral contact to encourage successful vertebral bone ingrowth thereby affixing thecap63 to a first orupper vertebra100 and the base61 to a second orlower vertebra100 in an adjacent pair ofvertebrae100. Thelower mesh66aand the upper mesh66bmay have the attributes of thelower mesh16aand theupper mesh16bdiscussed above with reference to the first preferred embodiment.

FIG. 6B shows a side sectional view of a third preferred embodiment of adisk prosthesis70 in accordance with the present invention. Thedisk prosthesis70 has adistal end70a, aproximal end70b, a lower wall70c, anupper wall70d, a first sidewall (not shown), and a second sidewall (not shown). The disk prosthesis includes a first part or acap73. Thecap73 includes a top73d, a bottom73chaving anopening73f, anouter surface73a, an inner surface73band asocket73eextending into an interior of thecap73 from the opening and defined by the inner surface73b. Theouter surface73aproximate the top73dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis70 further includes a second part or a base71 including a top71d, a bottom71c, and an outer surface71a. The outer surface71aproximate the bottom71ccontacts aconcave portion100aof asecond vertebra100, and the outer surface71aof the base71 proximate the top71dof the base71 cooperatively engages the inner surface73bof thecap73 thereby allowing at least two-degrees of freedom of movement.

When inserted into anintervertebral space121 thecap73 and the base71 function together as one overall device, i.e., thedisk prosthesis70. Thecap73 and the base71 are preferably not mechanically connected. Thebase71 is preferably not retained in thecap73, but could be. In alternate embodiments thecap73 and the base71 are connected by a flexible structure or element (not shown) or are totally encased in a pliable, bio-compatible slip-cover or pouch (not shown). The inner surface73band aportion71eof the outer surface71athat contacts the inner surface73bare preferably formed of or coated with a bio-compatible, smooth, low-friction material with high durability, such as a ceramic, an alloy or the like. The top71dof thebase71 includes a spherically or hemispherically-shaped portion or aball71f. Theball71fof the base71 cooperatively engages thesocket73eof thecap73 thereby mimicking a ball and shallow socket joint such as a shoulder-joint. Obviously, other iterations and combinations of mutually cooperating engagement designs providing relative movement could be implemented without departing from the broad general scope of the present invention.

The lower wall70cincludes alower mesh structure76aand theupper wall70dof thedisk prosthesis70 includes anupper mesh structure76bat the point of vertebral contact to encourage successful vertebral bone ingrowth thereby affixing thecap73 to a first orupper vertebra100 and the base71 to a second orlower vertebra100 in an adjacent pair ofvertebrae100. Thelower mesh76aand theupper mesh76bmay have the attributes of thelower mesh16aand theupper mesh16bdiscussed above with reference to the first preferred embodiment.

FIG. 6C shows a side sectional view of a fourth preferred embodiment of adisk prosthesis80 in accordance with the present invention. Thedisk prosthesis80 has adistal end80a, aproximal end80b, a lower wall80c, anupper wall80d, a first sidewall (not shown), and a second sidewall (not shown). The disk prosthesis includes a first part or acap83. Thecap83 includes a top83d, a bottom83chaving anopening83f, an outer surface83a, aninner surface83band asocket83eextending into an interior of thecap83 from the opening and defined by theinner surface83b. The outer surface83aproximate the top83dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis80 further includes a second part or a base81 including a top81d, a bottom81c, and an outer surface81a. The outer surface81aproximate the bottom81ccontacts aconcave portion100aof asecond vertebra100, and the outer surface81aof the base81 proximate the top81dof the base81 cooperatively engages theinner surface83bof thecap83 thereby allowing at least two-degrees of freedom of movement.

When inserted into anintervertebral space121 thecap83 and the base81 function together as one overall device, i.e., thedisk prosthesis80. Thecap83 and the base81 are preferably not mechanically connected. Thebase81 is preferably not retained in thecap83, but could be. In alternate embodiments thecap83 and the base81 are connected by a flexible structure or element (not shown) or are totally encased in a pliable, bio-compatible slip-cover or pouch (not shown). Theinner surface83band aportion81eof the outer surface81athat contacts theinner surface83bare preferably formed of or coated with a bio-compatible, smooth, low-friction material with high durability, such as a ceramic, an alloy or the like. The top81dof thebase81 includes a spherically or hemispherically-shaped portion or aball81f. Theball81fof the base81 cooperatively engages thesocket83eof thecap83 thereby mimicking a ball and shallow socket joint such as a shoulder-joint. Obviously, other iterations and combinations of mutually cooperating engagement designs providing relative movement could be implemented without departing from the broad general scope of the present invention.

The lower wall80cincludes alower mesh structure86aand theupper wall80dof thedisk prosthesis80 includes an upper mesh structure86bat the point of vertebral contact to encourage successful vertebral bone ingrowth thereby affixing thecap83 to a first orupper vertebra100 and the base81 to a second orlower vertebra100 in an adjacent pair ofvertebrae100. Thelower mesh86aand the upper mesh86bmay have the attributes of thelower mesh16aand theupper mesh16bdiscussed above with reference to the first preferred embodiment.

FIG. 7A shows thedisk prosthesis60 of the second preferred embodiment with a specially designedfirst insertion tool18 having a handle18aand a plurality of resilient graspingfingers19. The graspingfingers19 are actuated to grasp and hold thedisk prosthesis60 by moving a tool actuation stem17 proximally and to open and release thedisk prosthesis60 by moving the tool actuation stem17 distally. Thehandle18aof thefirst insertion tool18 may be formed of any substantially rigid material, but preferably is formed of a material that is bio-compatible such as titanium, stainless steel, or of a bio-compatible alloy, composite, polymeric material or the like. It should be noted that the material of construction of thehandle18aof thefirst insertion tool18 could be any material without diverging from the broad scope of the present invention. The graspingfingers19 are preferably formed of a resilient, bio-compatible synthetic or polymeric material. It is contemplated that the graspingfingers19 are biased by either their own resiliency or by other resilient means (not shown) such as coil springs in order to allow the graspingfingers19 to grasp thedisk prosthesis60 without actuation but to be capable of releasing the disk prosthesis by merely twisting or moving thefirst insertion tool18 proximally at a slight angle.

FIG. 7B shows thedisk prosthesis60 of the second preferred embodiment with a specially designedsecond insertion tool22 having a handle22aand asuction cup23. Thehandle22aof thesecond insertion tool22 may be formed of any substantially rigid material, but preferably is formed of a material that is bio-compatible such as titanium, stainless steel, or of a bio-compatible alloy, composite, polymeric material or the like. It should be noted that the material of construction of thehandle22aof thesecond insertion tool22 could be any material without diverging from the broad scope of the present invention. Thesuction cup23 is preferably formed of a resilient, bio-compatible synthetic or polymeric material. Preferably, thesuction cup23 is biased inwardly by its own resiliency in order to allow thesuction cup23 to grasp thedisk prosthesis60 without actuation but to be capable of releasing the disk prosthesis by merely twisting or moving thesecond insertion tool22 proximally at a slight angle.

FIG. 7C shows thedisk prosthesis60 of the second preferred embodiment with a specially designedthird insertion tool20 having a handle20aand being threaded into asocket64 withfemale threads64abymale threads20bof thethird insertion tool20. Thehandle20aof thethird insertion tool20 may be formed of any substantially rigid material, but preferably is formed of a material that is bio-compatible such as titanium, stainless steel, or of a bio-compatible alloy, composite, polymeric material or the like. It should be noted that the material of construction of thethird insertion tool20 could be any material without diverging from the broad scope of the present invention. Design of insertion tools are not critical to the present invention, and a variety of tool designs are contemplated for use with various disk prostheses.

FIGS. 11A–11B show a fifth preferred embodiment of a disk prosthesis in accordance with the present invention. Thedisk prosthesis90 has adistal end90a, aproximal end90b, alower wall90c, anupper wall90d, a first sidewall (not shown), and a second sidewall (not shown). The disk prosthesis includes a first part or acap93. Thecap93 includes a top93d, a bottom93chaving anopening93f, an outer surface93a, an inner surface93band asocket93eextending into an interior of thecap93 from the opening and defined by the inner surface93b. The outer surface93aproximate the top93dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis90 further includes a second part or a base91 including a top91d, a bottom91c, and an outer surface91a. The outer surface91aproximate the bottom91ccontacts aconcave portion100aof asecond vertebra100, and the outer surface91aof the base91 proximate the top91dof the base91 cooperatively engages the inner surface93bof thecap93 thereby allowing at least two-degrees of freedom of movement. Thecap93 is preferably slightly smaller than the base91 in both length and width in order to allow freedom movement even when bone growth reaches near the edges of thecap93 and/orbase91. Alternatively, thebase91 may be slightly smaller than thecap93 for similar reasons without departing from the present invention.

Further, thedisk prosthesis90 includes at least oneupper arch150 and at least onelower arch152, but preferably thedisk prosthesis90 includes threeupper arches150 and threelower arches152. Thearches150,152 are generally disposed symmetrically along and about a centerline of the longer axis of thedisk prosthesis90 and are secured to the body of thedisk prosthesis90. Of course thearches150,152 may be secured to thedisk prosthesis90 by other means and may be disposed in other orientations without departing from the spirit of the present invention. Preferably, thearches150,152 protrude above the top and bottom190d,190cof thedisk prosthesis90, respectively. Thearches150,152 are configured to settle into bone matter, and therefore, thearches150,152 have sharpened edges150a,152a. The sharpened edges150a,152amay include serrations, pins, sharpened cones or a simple knife-like edge, but need not be. Preferably, the sharpened edges150a,152aare partially knife like proximate the ends of the arches and partially covered with sharpenedcones153. Thearches150,152 are preferably about 0.5 mm to about 2.0 mm wide. Thearches150,152 also serve to center thedisk prosthesis90 during placement and prevent thedisk prosthesis90 from rolling or canting thereafter.

FIGS. 12A–12B show a sixth preferred embodiment of adisk prosthesis190 in accordance with the present invention. Thedisk prosthesis190 has adistal end190a, aproximal end190b, alower wall190c, anupper wall190d, afirst sidewall190e, and asecond sidewall190f. The disk prosthesis includes a first part or acap193. Thecap193 includes a top193d, a bottom193chaving anopening193f, an outer surface193a, an inner surface (not shown) and a socket (not shown) extending into an interior of thecap193 from the opening and defined by the inner surface. The outer surface193aproximate the top193dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis190 further includes a second part or a base191 including a top191d, a bottom191c, and an outer surface191a. The outer surface191aproximate the bottom191ccontacts aconcave portion100aof asecond vertebra100, and the outer surface191aof the base191 proximate the top191dof the base191 cooperatively engages the inner surface (not shown) of thecap193 thereby allowing at least two-degrees of freedom of movement. Further, thedisk prosthesis190 includes at least oneupper arch150 and at least onelower arch152, but preferably thedisk prosthesis190 includes threeupper arches150 and threelower arches152 similar to thedisk prosthesis90. Thearches150,152 are generally disposed symmetrically along and about a centerline of the longer axis of thedisk prosthesis190 and are secured to the body of thedisk prosthesis190. The top of thecap193 has a recess and the bottom of thebase191 has a recess, the recesses include aplatform193hand191h, respectively. Theplatforms191h,193hare preferably are texturized and/or coated with a material to promote bone growth.

FIGS. 13A–13B show a seventh preferred embodiment of adisk prosthesis290 in accordance with the present invention. Thedisk prosthesis290 has adistal end290a, aproximal end290b, alower wall290c, anupper wall290d, afirst sidewall290e, and asecond sidewall290f. The disk prosthesis includes a first part or acap293. Thecap293 includes a top293d, a bottom293chaving anopening293f, an outer surface293a, an inner surface (not shown) and a socket (not shown) extending into an interior of thecap293 from the opening and defined by the inner surface. The outer surface293aproximate the top293dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis290 further includes a second part or a base291 including a top291d, a bottom291c, and an outer surface291a. The outer surface291aproximate the bottom291ccontacts aconcave portion100aof asecond vertebra100, and the outer surface291aof the base291 proximate the top291dof the base291 cooperatively engages the inner surface (not shown) of thecap293 thereby allowing at least two-degrees of freedom of movement. Further, thedisk prosthesis290 includes at least oneupper arch150 and at least onelower arch152, but preferably thedisk prosthesis290 includes threeupper arches150 and threelower arches152 similar to thedisk prosthesis90. Thearches150,152 are generally disposed symmetrically along and about a centerline of the longer axis of thedisk prosthesis290 and are secured to the body of thedisk prosthesis290. The top of thecap293 and the bottom of the base291 are preferably flatly shaped. The flat surfaces preferably are texturized and/or coated with a material to promote bone growth.

FIGS. 14A–14B show an eighth preferred embodiment of adisk prosthesis390 in accordance with the present invention. Thedisk prosthesis390 has adistal end390a, aproximal end390b, alower wall390c, anupper wall390d, afirst sidewall390e, and asecond sidewall390f. The disk prosthesis includes a first part or acap393. Thecap393 includes a top393d, a bottom393c, an outer surface393a, an inner surface (not shown) and a socket (not shown) extending into an interior of thecap393 from the opening and defined by the inner surface393b. The outer surface393aproximate the top393dcontacts aconcave portion100bof afirst vertebra100. Thedisk prosthesis390 further includes a second part or a base391 including a top391d, a bottom391c, and an outer surface391a. The outer surface391aproximate the bottom391ccontacts aconcave portion100aof asecond vertebra100, and the outer surface391aof the base391 proximate the top391dof the base391 cooperatively engages the inner surface (not shown) of thecap393 thereby allowing at least two-degrees of freedom of movement. Further, thedisk prosthesis390 includes at least one row of sharpenedcones153 on the top of thecap393 and at least one row of sharpenedcones153 on the bottom of thebase391, but preferably thedisk prosthesis390 includes three rows of sharpenedcones153 on the top of thecap393 and three rows of sharpenedcones153 on the bottom of thebase391. The rows of sharpenedcones153 are generally disposed symmetrically along and about a centerline of the longer axis of thedisk prosthesis390 and are secured to the body of thedisk prosthesis390. The top of thecap393 and the bottom of the base391 are preferably convexly shaped to more readily find the contours of theconcave portions100a,100bofadjacent vertebrae100. Preferably, the surface of thedisk prosthesis390 proximate the rows of sharpenedcones153 is texturized and/or coated with a material to promote bone growth such as hydroxyapatite.

FIGS. 15A–15B show afourth insertion tool220 for a disk prosthesis10 (60,70, or80) having lower andupper openings16a,16b(66a,66b,76a,76b,86a,86b), respectively. Theinsertion tool220 has afirst finger224 configured to cooperatively engage thelower opening16aand asecond finger222 configured to cooperatively engage theupper opening16b. Thefingers222,224 have outer surfaces which are shaped to match the contoured shape of thedisk prosthesis10 to allow a smooth insertion of thedisk prosthesis10. The combination of theinsertion tool220 and thedisk prosthesis10 when the first andsecond fingers222,224 are engaged with theingrowth openings16a,16b, forms a combined structure having generally rounded exposed surfaces. Thefingers222,224 also prevent foreign matter and debris from getting caught in theopenings16a,16bduring insertion. Because thefingers222,224 grasp thedisk prosthesis10 in a specific orientation defined by the upper andlower openings16a,16b, theinsertion tool220 provides the surgeon with means to orient thedisk prosthesis10 correctly during insertion.

Theinsertion tool220 further includes a drivingmember226 that is configured to engage the body of thedisk prosthesis10. The drivingmember226 is configured to be impacted such that during insertion a surgeon may tap or hammer the drivingmember226 to push thedisk prosthesis10 through a small opening. Preferably, the first andsecond fingers222,224 are retractable relative to the drivingmember226. Thus, after thedisk prosthesis10 is inserted to a desired position, the first andsecond fingers222,224 are retracted while the drivingmember226 holds thedisk prosthesis10 in place. Optionally, thedisk prosthesis10 may have grooves166 (shown in phantom inFIG. 15B) extending from the upper andlower openings16a,16bto facilitate the removal of theretractable fingers222,224. Optionally, theinsertion tool220 includes third and fourth fingers228 (shown in phantom inFIGS. 15A–15B) configured to retractably move along the space between theupper part13 and thelower part11 of the body of thedisk prosthesis10.

FIGS. 16A–16B is a side elevational view of afifth insertion tool230 for a disk prosthesis90 (190,290 or390) having upper and lower openings96a,96band upper andlower arches150,152. For example, theupper finger232 has first andsecond prongs232a,232bfor straddling theupper arches150 as best seen inFIG. 16B. Theinsertion tool230 is similar to theinsertion tool220, but each of theretractable fingers232,234 is forked to accommodate thearches150,152. Preferably, thearches150,152 and the rows ofcones153 are just below the outer surface of thefingers232,234, so that thearches150,152 do not injure adjacent tissue during insertion. Optionally, theinsertion tool230 includes third and fourth fingers238 (shown in phantom inFIGS. 16A–16B) configured to retractably move between the space between theupper part93 and thelower part91 of the body of thedisk prosthesis90. Furthermore, it would be obvious to one skilled in the art to utilize multiple prongs in each of theretractable fingers232,234 in order to accommodatemultiple arches150,152 (such as ondisk prostheses190 and290) and multiple rows of sharpened cones153 (such as on disk prosthesis390).

Preferably, theintervertebral disk prostheses10,60,70,90,190,290 and390 have a freedom of movement that is limited to between about 2–15 degrees tilt in any direction. The annular ligament of a human being is built for physiologic limiting thereby stopping over rotation. The facets in the lumbar region also limit rotation and tilt.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims (20)

1. An intervertebral disk prosthesis having a convexly tapered distal end, a convexly tapered proximal end, an anterior side and a posterior side, the intervertebral disk prosthesis further comprising:

an upper part including a convexly-shaped and rounded top, a bottom having an opening, an outer surface, an inner surface and a socket extending into an interior of the upper part from the opening, the outer surface proximate the top being configured to contact a concave portion of a first vertebra; and

a lower part including a top, a convexly-shaped and rounded bottom, and an outer surface, the outer surface proximate the bottom being configured to contact a concave portion of a second vertebra that is adjacent to the first vertebra, and the outer surface of the lower part proximate the top of the lower pan being cooperatively and movably overlapped by the inner surface of the upper part thereby allowing at least two-degrees of freedom of movement,

the taper of the distal end diminishing more gradually than the taper of the proximal end, and

the anterior and posterior sides are at least partially convexly shaped in order to allow installation of the intervertebral disk prosthesis into a space defined by the concavities of the adjacent first and second vertebrae.

2. The intervertebral disk prosthesis ofclaim 1, wherein the top of the upper part has an ingrowth opening to encourage vertebral ingrowth and is configured to align the intervertebral disk prosthesis within an intervertebral space.

3. The intervertebral disk prosthesis ofclaim 2, further comprising a generally continuous sheet of biocompatible porous material at least partially spanning the ingrowth opening.

4. The intervertebral disk prosthesis ofclaim 3, wherein the porous material is hydroxyapatite-coated metal.

5. The intervertebral disk prosthesis ofclaim 2, further comprising a mesh structure at least partially spanning the ingrowth surface.

6. The intervertebral disk prosthesis ofclaim 1, wherein the bottom of the lower part has an ingrowth opening to encourage vertebral ingrowth and is configured to align the intervertebral disk prosthesis within an intervertebral space.

7. The intervertebral disk prosthesis ofclaim 6, further comprising a generally continuous sheet of biocompatible porous material at least partially spanning the ingrowth surface.

8. The intervertebral disk prosthesis ofclaim 7, wherein the porous material is hydroxyapatite-coated metal.

9. The intervertebral disk prosthesis ofclaim 6, further comprising a mesh structure at least partially spanning the ingrowth surface.

10. The intervertebral disk prosthesis ofclaim 1, wherein the distal end of the intervertebral prosthesis is generally bluntly rounded.

11. The intervertebral disk prosthesis ofclaim 1, wherein the proximal end of the intervertebral prosthesis is generally bluntly rounded.

12. The intervertebral disk prosthesis ofclaim 1, wherein an exterior surface of the intervertebral prosthesis is generally rounded.

13. The intervertebral disk prosthesis ofclaim 1, wherein the intervertebral prosthesis is formed at least partially of a biocompatible material selected from the group consisting of stainless steel, titanium, cobalt-chrome alloy, nickel plated metal, a biocompatible alloy, a biocompatible ceramic, and a biocompatible polymeric material.

14. The intervertebral disk prosthesis ofclaim 1, further comprising a pliable, biocompatible slip-cover that covers at least a portion of the upper part and a portion of the lower part, the slip-cover being configured to flexibly retain the movably coupled upper and lower parts.

15. The intervertebral disk prosthesis ofclaim 1, wherein the length of the intervertebral prosthesis as measured from the distal end to the proximal end is between about 10 mm and about 30 mm.

16. The intervertebral disk prosthesis ofclaim 1, wherein the width of the intervertebral prosthesis as measured between the anterior side and the posterior side is between about 10 mm and about 25 mm.

17. The intervertebral disk prosthesis ofclaim 1, wherein the height of the intervertebral prosthesis as measured between the top of the upper part and the bottom of the lower part is between about 5 mm and about 25 mm.

18. The intervertebral disk prosthesis ofclaim 1, wherein the freedom of movement is limited to between about 2–15 degrees tilt in any direction.

19. The intervertebral disk prosthesis ofclaim 1, wherein the disk prosthesis minimizes translational movement.

20. An intervertebral disk prosthesis having a convexly tapered distal end, a convexly tapered proximal end, anterior side and a posterior side, the intervertebral disk prosthesis further comprising:

a lower part including a convexly-shaped and rounded bottom, a top having an opening, an outer surface, an inner surface and a socket extending into an interior of the lower part from the opening, the outer surface proximate the bottom being configured to contact a concave portion of a first vertebra; and

an upper part including a bottom, a convexly-shaped and rounded top, and an outer surface, the outer surface proximate the top being configured to contact a concave portion of a second vertebra that is adjacent to the first vertebra, and the outer surface of the lower part proximate the bottom of the upper part being cooperatively and movably overlapped by the inner surface of the upper part thereby allowing at least two-degrees of freedom of movement,

the taper of the distal end diminishing more gradually than the taper of the proximal end, and

the anterior and posterior sides are at least partially convexly shaped in order to allow installation of the intervertebral disk prosthesis into a space defined by the concavities of the adjacent first and second vertebrae.

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